The yield strength anomaly of single-slip-oriented Fe–Al single crystals

Many features of the well-documented yield strength anomaly in B2-structured Fe–Al alloys have been successfully described or predicted by the vacancy-hardening model [George EP, Baker I. Philos Mag 1998;A77: 737]. Interestingly, the model does not predict any orientation dependence for the yield anomaly. Here, we examine this by measuring the yield stress of three different single-slip-oriented Fe–43Al single crystals as a function of temperature. It was found that the critical resolved shear stress of all the alloys decreased rapidly with temperature from 77 K to ∼300 K, showed a plateau from 300 K to 723 K, increased to a peak at 873 K, and then decreased again with further increase in temperature. While neither the low-temperature strength (<300 K) nor the temperature of the yield stress peak depended on the orientation (in agreement with the vacancy-hardening model), the yield stress in the plateau region around room temperature did.